1. Field of the Disclosure
The disclosure generally relates to reference-less repeaters, including techniques to estimate a wide range of frequencies in a digital signal and propagate frequency information with digital control.
2. Related Art
Reference-less repeaters provide significant advantages over repeaters requiring external frequency references. Dedicated frequency references typically need additional components that require additional power, mounting, board space, and environmental requirements in order to operate in a stable and effective manner. Schemes to distribute a common frequency reference among a variety of circuits to minimize these issues impose further shielding and isolation requirements on reference signal distribution circuits and board traces. Therefore, retiming circuits that eliminate the need for external frequency references provide significant power, layout, and physical isolation advantages.
Current reference-less repeaters typically employ high-power analog-only solutions that while having a wide frequency detection range, also have difficulty adapting to oversampling. Furthermore, analog-only reference-less repeaters have difficulty transferring frequency information from one node to another, and adapting to lower data rates typically used for auto-negotiation. Analog-only retiming circuits typically employ analog frequency detectors that consume large amounts of power. Digitally controlled reference-less retiming circuits, on the other hand, have a relatively narrow frequency detection range, but typically consume significantly less power than analog retiming circuits. Furthermore, digitally controlled reference-less retiming circuits provide data rate flexibility, particularly at lower data rates. Due to the narrow frequency detection range of digitally controlled reference-less retiming circuits, frequency estimation allows these circuits to quickly determine the frequency of an input signal, and distribute the frequency information quickly and efficiently.
Embodiments of the disclosure will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.